The present invention is directed to swinging bob toys, more particularly to swinging bob toys where the middle bob does not have a cylindrically-symmetric weight distribution, and even to swinging bob toys where the middle bob has few or no weight-distribution symmetries. One group of embodiments of particular importance for swinging bob toys where the weight distribution of the middle bob does not have cylindrical symmetry is swinging bob toys where the middle bob includes functional, internal components, such as one or more light-emitting elements powered by one or more electric batteries.
As shown in FIG. 1A, a swinging bob toy (100) consists of an end bob (110) and a cylindrically-symmetric bored bob (111) on a string (120). The end bob (110) is fixed at an end (121) of the string (120). The bored bob (111) has a bore (130) through which the string (120) passes, thereby allowing the bored bob (111) to slide freely along the string (120). As shown in FIG. 1B, the toy (100) is operated by holding the end (122) of the string opposite the end (121) where the end bob (110) is attached, and oscillating the hand (141) to cause the bobs (110) and (111) to separate and the end bob (110) to orbit about the bored bob (111). The bobs (110) and (111) can describe a vertical orbit (190), as shown in FIG. 11B, or horizontal orbits, figure-eight type orbits or irregular paths.
The above-described swinging bob toy (100) is described in German Patent No. 572723 issued in February of 1934, and a version of this toy (100) was marketed by Playco Plastics of Lincoln, Mass. under the trademark xe2x80x9cOYxe2x80x94OY.xe2x80x9d It should be noted that the German patent and Playco Plastics teach that the density of the bored bob (111) is cylindrically symmetric about the bore axis (136) and has a homogeneous density. A disadvantage of the homogeneous density of the bored bob (111) is that the string (120) tends to snag around the bored bob (111) as the bobs (110) and (111) orbit, inhibiting the enjoyment of operation of the toy (100).
An improved version of the swinging bob toy (200) is described in U.S. Pat. No. Re. 34,208 issued Mar. 30, 1993. As shown in FIG. 2, the improved swinging bob toy (200) consists of three bobs (210), (211) and (212) on a string (220), with end bobs (210) and (212) being fixed at the ends (221) and (222) of the string (220), and the middle bob (211) having a bore (230) through which the string (220) passes, thereby allowing the middle bob (211) to slide along the string (220). Having a bob (210)/(212) fixed at each end (221)/(222) of the string (220) allows a player to hold either end bob (210)/(212) during operation and perform juggling tricks, such as switching end bobs (210)/(212) in mid-air. (In this paragraph and the remainder of the Background of Invention section, the 200-series reference numerals of FIGS. 2, 3A and 3B, rather than the 100-series reference numerals of FIGS. 1A and 1B, will be used in discussions of swinging bob toys. Furthermore, components of the swinging bob toy other than those of the middle bob (211) will be assigned 200-series reference numerals corresponding to the 100-series reference numerals of FIGS. 1A and 1B.)
As shown in the cut-away view of the middle bob (211) of FIG. 3A and the cross-sectional view of FIG. 3B, one of the innovations of the swinging bob toy (200) of U.S. Pat. No. Re. 34,208 is a high-density weight (240) centered within a low-density surrounding material (250). In a swinging bob toy marketed under the trademark AstroJax(copyright), and having been distributed by New Toy Classics of San Francisco, Calif., United States, and Active People of Benningen, Switzerland, the weight (240) is made of brass and is essentially cylindrical with a central bore (232) along the axis of cylindrical symmetry (235) (i.e., the xe2x80x9cpolar axisxe2x80x9d) of the bob (211). The material (250) surrounding the weight (240) is a soft foam having a density of roughly 0.4 g/cc. The exterior surface (251) of the foam bob (211) is spherical, with the exception of two conical-section indents (231) at the top and bottom which lead to the bore (232) of the weight. The bore (230) of the bob (211) consists of the indents (231) in combination with the bore (232) of the weight (240). The mouth (234) of each conical-section indent (231) is rounded to meet the outside spherical surface (251).
The function of the high-density weight (240) is to concentrate the mass near the center of the bob (211), providing a low moment of inertia I about axes perpendicular to the polar axis (235), thereby allowing the middle bob (211) to rotate rapidly as the swinging outer bob (212) describes the top (291) of its orbit (290). This is the same principle that a diver uses when she tucks into a bob during a dive to complete more rotations, or an ice skater uses when he brings his anus in during a spin to rotate faster.
A particularly popular embodiment of the swinging bob toy (200) is a glow-in-the-dark version where the foam (250) surrounding the central weight (240) is impregnated with a phosphorescent pigment. When the phosphorescent pigment is exposed to light, the energy is absorbed and stored by the pigment, and then re-emitted as light over a period of ten to fifteen minutes. A user may therefore xe2x80x98chargexe2x80x99 up the bobs (210), (211) and (212) under bright light, and then play with the luminescent bobs (210), (211) and (212) in a dark area for the ten to fifteen minutes during which the bobs (210), (211) and (212) re-emit light. This provides the swinging bob toy (200) in its purest visual form, since the surrounding environment, and even the string (220) connecting the bobs (210), (211) and (212), is not visible.
The glow-in-the-dark embodiment of the swinging bob toy (200) has been enjoyed by children, as well as adults playing in nightclubs and rave parties. However, its enjoyment and popularity is limited by the inconvenience of needing to frequently recharge the pigment in the bobs (210), (211) and (212). Therefore, there has been demand for a battery-powered, light-emitting embodiment of the swinging bob toy (210), (211) and (212) for several years.
As discussed in U.S. Pat. No. Re. 34,208, a crucial measure of the xe2x80x9cgoodness of operationxe2x80x9d of a swinging bob toy (200) is the dimensionless ratio X given by
X=(mh2/I)1/2,xe2x80x83xe2x80x83(1.1) 
where I is the moment of inertia about axes perpendicular to the polar axis (235), m is the mass of each bob, and h is the height of the bore. It should be noted that this expression is only applicable for a middle bob (211) having cylindrical symmetry, so that the moment of inertia I is not a function of the azimuthal angle xcfx86 of the axis of rotation for which the moment of inertia I is calculated. If X is much greater than unity, the middle bob (211) can rotate rapidly in response to the torque produced by the string (220), and so the string (220) will not snag around the middle bob (211) and the motion will be smooth. However, if X is much less than unity, the middle bob (211) cannot rotate rapidly in response to the torque produced by the string (220), and so the string (220) will tend to snag, or even tangle, around the middle bob (211), disrupting the orbital motions of the bobs (210) and (211) and inhibiting enjoyment of the toy (200).
The design of a light-up version of the swinging bob toy (200) is further complicated by the fact that the functional, internal components in the middle bob (211) will typically produce a mass distribution which is not cylindrically symmetric, and may even have few or no symmetries. Furthermore, the functional, internal components will generally have considerable mass, and it will be difficult or impossible to position the functional, internal components near the center of the bob due to their dimensions.
Therefore, it is an object of the present invention is to provide a swinging bob toy having a middle bob without a cylindrically-symmetric weight distribution which has a moment of inertia as a function of azimuthal angle which prevents snagging or tangling of the string about the middle bob.
It is another object of the present invention is to provide a swinging bob toy having a middle bob without a cylindrically-synmmetric weight distribution which has one or more low moments of inertia.
It is another object of the present invention is to provide a swinging bob toy with a middle bob having weight-distribution symmetries producing one or more low moments of inertia.
It is another object of the present invention is to provide a swinging bob toy with a middle bob having few or no weight-distribution symmetries which has one or more low moments of inertia.
It is another object of the present invention is to provide a swinging bob toy having a middle bob without a cylindrically-symmetric weight distribution which has a minimum in variation of the moment of inertia as a function of axis of rotation.
It is another object of the present invention is to provide a swinging bob toy with a middle bob having weight-distribution symmetries which has a minimum in variation of the moment of inertia as a function of axis of rotation.
It is another object of the present invention is to provide a swinging bob toy with a middle bob having few or no weight-distribution symmetries which has a minimum in variation of the moment of inertia as a function of axis of rotation.
Moreover, it is an object of the present invention to provide some or all of the above-listed objects for a middle bob having functional, internal components.
It is another object of the present invention is to provide a swinging bob toy having a middle bob with functional, internal components which includes a means for securing top and bottom halves of the middle bob, and which has one or more low moments of inertia.
It is another object of the present invention to provide a light-emitting toy having a dramatic appearance.
It is another object of the present invention is to provide a battery-powered light-emitting embodiment of the swinging bob toy.
It is another object of the present invention is to provide a light-emitting swinging bob toy where the lights flash at a frequency that is rapid enough that the flashing cannot be detected by the human eye when the bobs are stationary, but becomes detectable when the bobs have a velocity associated with normal play.
Furthermore, it is an object of the present invention is to provide a light-emitting swinging bob toy where the lights appear not to flash when the bobs are stationary, but appear to flash when the bobs have a velocity associated with normal play, where this change in appearance is accomplished without use of a motion detecting mechanism.
Also, it is an object of the present invention is to provide a light-emitting swinging bob toy where the lights appear not to flash when the bobs are stationary, but appear to flash when the bobs have a velocity associated with normal play, where this change in appearance is accomplished by taking advantage of the physiological and/or psychophysiological qualities of human visual perception.
It is another object of the present invention is to provide a battery-powered light-emitting embodiment of the swinging bob toy having one or more of the above-listed objects.
Additional objects and advantages of the invention will be set forth in the description which follows, and will be apparent from the description or may be learned from the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the claims.
The present invention is directed to a swinging bob toy having a first bob attached at the end of a string, and a second bob having a bore through which the string passes, allowing the second bob to slide along the string. The second bob has a mass distribution which does not have cylindrical symmetry about an axis along the bore, i.e., the polar axis. The percentage moment variation V is defined as
V=100xc3x97[I(xcfx86max)xe2x88x92I(xcfx86min)]/I(xcfx86max), 
where xcfx86 is the azimuthal angle of an axis of rotation in the equatorial plane normal to the polar axis, xcfx86max is the azimuthal angle of the axis of rotation at which the moment of inertia I has its maximum value, and xcfx86min is the azimuthal angle of the axis of rotation at which the moment of inertia I has its minimum value. The percentage moment variation V has a value of less than 66%, and the mass distribution has a center of mass located near the middle of the bore axis.
The present invention is directed to a swinging bob toy having a first bob attached at the end of a string of length l, and a second bob having a bore through which the string passes, allowing the second bob to slide along the string. A light in one of the bobs is connected to circuitry to produce a flashing of the light at a rate N, with the light being off for a fraction xcex1 of the flashing cycle. If the viewer is a distance D from the swinging bob toy, the flashing occurs at a rate N within the bounds
10Hz less than N less than 200xcex1{overscore (gl)}/D, 
where g is the acceleration due to gravity, so that said flashing is not visible when the light is stationary, but is visible during operation of the toy.